Abrasion test methods and devices

ABSTRACT

A method according to one embodiment includes measuring an initial coating thickness on a tape bearing surface of a module in a carrier, running a tape across the tape bearing surface, and at intervals, measuring a residual thickness of the coating.

BACKGROUND

The present invention relates to media abrasivity testing, and moreparticularly, this invention relates to an improvement in the testing ofmedia abrasivity and/or coating wear.

In magnetic storage systems, data is read from and written onto magneticrecording media utilizing magnetic transducers commonly. Data is writtenon the magnetic recording media by moving a magnetic recordingtransducer to a position over the media where the data is to be stored.The magnetic recording transducer then generates a magnetic field, whichencodes the data into the magnetic media. Data is read from the media bysimilarly positioning the magnetic read transducer and then sensing themagnetic field of the magnetic media. Read and write operations may beindependently synchronized with the movement of the media to ensure thatthe data can be read from and written to the desired location on themedia.

An important and continuing goat in the data storage industry is that ofincreasing the density of data stored on a medium. For tape storagesystems, that goal has led to increasing the track and linear bitdensity on recording tape, and decreasing the thickness of the magnetictape medium. However, the development of small footprint, higherperformance tape drive systems has created various problems in thedesign of a tape head assembly, as well as tapes, for use in suchsystems.

Media abrasivity is directly related to head wear, recession, andspacing loss. The current method employed by media vendors to gaugeabrasivity involves methods which have been shown to not berepresentative of actual head wear, and a poor gauge of tape abrasivity.

SUMMARY

A method according to one embodiment includes measuring an initialcoating thickness on a tape bearing surface of a module in a carrier,running a tape across the tape bearing surface, and at intervals,measuring a residual thickness of the coating.

Other aspects and embodiments of the present invention will becomeapparent from the following detailed description, which, when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a simplified tape drive systemaccording to one embodiment.

FIG. 2 illustrates a side view of a flat-lapped, bi-directional, twomodule magnetic tape head according to one embodiment.

FIG. 2A is a tape bearing surface view taken from Line 2A of FIG. 2.

FIG. 2B is a detailed view taken from Circle 2B of FIG. 2A,

FIG. 2C is a detailed view of a partial tape bearing surface of a pairof modules.

FIG. 3 depicts a method according to one embodiment.

FIG. 4A is a partial cross-sectional view of a tape head according toone embodiment.

FIG. 4B is a partial cross-sectional view of a tape head according toone embodiment.

FIG. 5 is a top-down view of a coating scheme according to oneembodiment.

FIG. 6A is a partial top-down view of a coating thickness measuringdevice according to one embodiment.

FIG. 6B is a partial cross-sectional view of a coating thicknessmeasuring device according to one embodiment.

FIG. 7A is a partial top-down view of a coating thickness measuringdevice according to one embodiment.

FIG. 7B is a partial cross-sectional view of a coating thicknessmeasuring device according to one embodiment.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless otherwise specified.

The following description discloses several preferred embodiments ofmagnetic storage systems, as well as operation and/or component partsthereof.

In one general embodiment, a system includes a carrier for receiving amodule; a transport mechanism for running a tape across a tape bearingsurface of the module; and a measuring device for measuring an extent ofwear of a coating on a tape bearing surface of the module.

In another general embodiment, a module includes a body having a tapebearing surface, the body having an approximate tape bearing surfaceprofile and dimensions as a module of interest; and a coating on thetape bearing surface.

In another general embodiment, a method includes measuring an initialcoating thickness on a tape bearing surface of a module in a carrier;running a tape across the tape bearing surface; and at intervals,measuring a residual thickness of the coating.

FIG. 1 illustrates a simplified tape drive 100 of a tape-based datastorage system, which may be employed in the context of the presentinvention. While one specific implementation of a tape drive is shown inFIG. 1, it should be noted that the embodiments described herein may beimplemented in the context of any type of tape drive system.

As shown, a tape supply cartridge 120 and a take-up reel 121 areprovided to support a tape 122. One or more of the reels may form partof a removable cartridge and are not necessarily part of the system 100.The tape drive, such as that illustrated in FIG. 1, may further includedrive motor(s) to drive the tape supply cartridge 120 and the take-upreel 121 to move the tape 122 over a tape head 126 of any type. Suchhead may include an array of readers, writers, or both.

Guides 125 guide the tape 122 across the tape head 126. Such tape head126 is in turn coupled to a controller assembly 128 via a cable 130. Thecontroller 128 typically controls head functions such as servofollowing, writing, reading, etc. The controller may operate under logicknown in the art, as well as any logic disclosed herein. The cable 130may include read/write circuits to transmit data to the head 126 to berecorded on the tape 122 and to receive data read by the head 126 fromthe tape 122. An actuator 132 controls position of the head 126 relativeto the tape 122.

An interface 134 may also be provided for communication between the tapedrive and a host (integral or external) to send and receive the data andfor controlling the operation of the tape drive and communicating thestatus of the tape drive to the host, all as will be understood by thoseof skill in the art.

By way of example, FIG. 2 illustrates a side view of a flat-lapped,bi-directional, two-module magnetic tape head 200 which may beimplemented in the context of the present invention. As shown, the headincludes a pair of modules 204, each equipped with bases 202, and fixedat a small angle α with respect to each other. The bases may be“U-beams” that are adhesively coupled together. Each module 204 includesa substrate 204A and a closure 204B with a thin film portion, commonlyreferred to as a “gap” in which the readers and/or writers 206 areformed. In use, a tape 208 is moved over the modules 204 along a media(tape) bearing surface 209 in the manner shown for reading and writingdata on the tape 208 using the readers and writers. The wrap angle θ ofthe tape 208 at edges going onto and exiting the flat media supportsurfaces 209 are usually between about 0.1 degree and about 5 degrees.

The substrates 204A are typically constructed of a wear resistantmaterial, such as a ceramic. The closures 204B made of the same orsimilar ceramic as the substrates 204A.

The readers and writers may be arranged in a piggyback or mergedconfiguration. An illustrative piggybacked configuration comprises a(magnetically inductive) writer transducer on top of (or below) a(magnetically shielded) reader transducer (e.g., a magnetoresistivereader, etc.), wherein the poles of the writer and the shields of thereader are generally separated. An illustrative merged configurationcomprises one reader shield in the same physical layer as one writerpole (hence, “merged”). The readers and writers may also be arranged inan interleaved configuration. Alternatively, each array of channels maybe readers or writers only. Any of these arrays may contain one or moreservo track readers for reading servo data on the medium.

FIG. 2A illustrates the tape bearing surface 209 of one of the modules204 taken from Line 2A of FIG. 2. A representative tape 208 is shown indashed lines. The module 204 is preferably long enough to be able tosupport the tape as the head steps between data bands.

In this example, the tape 208 includes 4 to 22 data bands, e.g., with 16data bands and 17 servo tracks 210, as shown in FIG. 2A on a one-halfinch wide tape 208. The data bands are defined between servo tracks 210.Each data band may include a number of data tracks, for example 512 datatracks (not shown). During read/write operations, the readers and/orwriters 206 are positioned to specific track positions within one of thedata bands. Outer readers, sometimes called servo readers, read theservo tracks 210. The servo signals are in turn used to keep the readersand/or writers 206 aligned with a particular set of tracks during theread/write operations.

FIG. 2B depicts a plurality of readers and/or writers 206 formed in agap 218 on the module 204 in Circle 2B of FIG. 2A. As shown, the arrayof readers and writers 206 includes, for example, 16 writers 214, 16readers 216 and two servo readers 212, though the number of elements mayvary. Illustrative embodiments include 8, 16, 32, 40, and 64 readersand/or writers 206 per array. A preferred embodiment includes 32 readersper array and/or 32 writers per array, where the actual number oftransducing elements could be greater, e.g., 33, 34, etc. This allowsthe tape to travel more slowly, thereby reducing speed-induced trackingand mechanical difficulties and/or execute fewer “wraps” to fill or readthe tape. While the readers and writers may be arranged in a piggybackconfiguration as shown in FIG. 2B, the readers 216 and writers 214 mayalso be arranged in an interleaved configuration. Alternatively, eacharray of readers and/or writers 206 may be readers or writers only, andthe arrays may contain one or more servo readers 212. As noted byconsidering FIGS. 2 and 2A-B together, each module 204 may include acomplementary set of readers and/or writers 206 for such things asbi-directional reading and writing, read-while-write capability,backward compatibility, etc.

FIG. 2C shows a partial tape bearing surface view of complimentarymodules of a magnetic tape head 200 according to one embodiment. In thisembodiment, each module has a plurality of read/write (R/W) pairs in apiggyback configuration formed on a common substrate 204A and anoptional electrically insulative layer 236. The writers, exemplified bythe write head 214 and the readers, exemplified by the read head 216,are aligned parallel to a direction of travel of a tape mediumthereacross to form an R/W pair, exemplified by the R/W pair 222.

Several R/W pairs 222 may be present, such as 8, 16, 32 pairs, etc. TheR/W pairs 222 as shown are linearly aligned in a direction generallyperpendicular to a direction of tape travel thereacross. However, thepairs may also be aligned diagonally, etc. Servo readers 212 arepositioned on the outside of the array of R/W pairs, the function ofwhich is well known.

Generally, the magnetic tape medium moves in either a forward or reversedirection as indicated by arrow 220. The magnetic tape medium and headassembly 200 operate in a transducing relationship in the mannerwell-known in the art. The piggybacked MR head assembly 200 includes twothin-film modules 224 and 226 of generally identical construction.

Modules 224 and 226 are joined together with a space present betweenclosures 204B thereof (partially shown) to form a single physical unitto provide read-while-write capability by activating the writer of theleading module and reader of the trailing module aligned with the writerof the leading module parallel to the direction of tape travel relativethereto. When a module 224, 226 of a piggyback head 200 is constructed,layers are formed in the gap 218 created above an electricallyconductive substrate 204A (partially shown), e.g., of AlTiC, ingenerally the following order for the R/W pairs 222: an insulating layer236, a first shield 232 typically of an iron alloy such as NiFe(permalloy), CZT or Al—Fe—Si (Sendust), a sensor 234 for sensing a datatrack on a magnetic medium, a second shield 238 typically of anickel-iron alloy (e.g., 80/20 Permalloy), first and second writer poletips 228, 230, and a coil (not shown).

The first and second writer poles 228, 230 may be fabricated from highmagnetic moment materials such as 45/55 NiFe. Note that these materialsare provided by way of example only, and other materials may be used.Additional layers such as insulation between the shields and/or poletips and an insulation layer surrounding the sensor may be present.Illustrative materials for the insulation include alumina and otheroxides, insulative polymers, etc.

Each drive product has different generations and each generationtypically results in creation of a newly formulated tape that is usuallysmoother, less abrasive and has denser magnetic particle packing thanthe previous generation.

The current method employed by media vendors to gauge tape abrasivityinvolves running tape over the tip of a triangular shaped AlFeSil wearbar. This method has been shown to be not representative of actual headwear, and not a good gauge of tape abrasivity.

According to a preferred embodiment, a testing system and/or methodologymay be used for gauging media abrasivity relative to particular types ofmodules. Various approaches disclosed herein more accurately measuremedia abrasivity and/or are more representative of the head wearobserved in actual product usage, in addition to being fast, accurate,and easy to use.

Now referring to FIG. 3, a method 300 includes measuring an initialcoating thickness on a tape bearing surface of a module in a carrier,the module having an approximate tape bearing surface profile anddimensions as a module of interest. See operation 302. Illustrativedevices for performing the measuring are described below.

In a preferred approach, a “module of interest” may be any functionalmodule that is in production, may go into production, or simply has ashape similar to a module that will be used in a product.

In one embodiment, a module that may be used in the testing may includea body having a tape bearing surface. In a preferred approach, the bodymay have an approximate tape bearing surface profile and dimensions as amodule of interest. In another approach, the module may be an operativemodule for a tape head according to any of the embodiments describedand/or suggested herein, e.g., one of the modules of interest. In oneparticular approach, the module may additionally include a coating onthe tape bearing surface.

Moreover, a module that looks like a tape head, but without any of therecording elements may be used to reduce the production time and cost ofthe testing platform. Thus, in one approach, the module may benonfunctional, as in a case where the module may be a dummy module, areplica, a defective real module, etc.

In various approaches of method 300, the module may incorporate any ofthe modules mentioned and/or suggested herein. In another approach, themodule may be part of a completed head assembly according to any of theembodiments described and/or suggested herein. In one approach, the headassembly may be received in the carrier.

In various approaches, the carrier may include plastic, glass, ceramic,metal, etc. or any other material which would be apparent to one skilledin the art upon reading the present description. Moreover, the carriermay include a coupling mechanism such as a slot, clamp, etc. forcoupling the module to the carrier.

With continued reference to FIG. 3, the method 300 additionally includesrunning a tape across the tape bearing surface of the module. Seeoperation 304. According to various approaches, the tape may include anewly formulated tape, a tape from a previous generation, a tapeselected from a bank of tapes, etc.

In operation 306, a residual thickness of the coating is measured atregular and/or nonregular intervals. For example, the tape may be runfor a short period, and then a coating wear measurement may be taken,followed by running the tape again for a second period and re-measuring,and so on. In one approach, an initial coating thickness may be takenbefore the tape is run across the coating to be used as a baseline whencomparing later coating wear measurements.

In one approach, the measuring may be performed using any of themeasuring devices mentioned and/or suggested herein. According toanother approach, the module may be removed from the carrier for theconducting the measuring.

Referring now to FIG. 4A, a system 400 includes a carrier 402 which maybe for receiving a module 204. The system 400 additionally includes atransport mechanism 404 which may be for running a tape 406 across atape bearing surface 209 of the module 204.

The module has a coating 414 thereon that wears when the tape is runthereacross due to atmospheric pressure forcing the tape against thesubambient interface between the module and the tape. The corners of themodule serve to skive air from the tape to create the subambientcondition. See also coating 414 of FIGS. 6B and 7B. An extent of thewear of the coating is indicative of the expected wear of the module ofinterest.

During tape wear testing, the tape is run across the module, and anextent of wear of the coating is measured. Illustrative methods forperforming the coating measurements are described herein.

With continued reference to FIG. 4A, the system 400 additionallyincludes a measuring device 412 for measuring an extent of wear of thecoating 414 on the tape bearing surface 209 of the module 204.

In accordance with various approaches, the measuring device 412 mayinclude an ellipsometer, a stylus profiler, etc. or any other measuringdevice which would be apparent to one skilled in the art upon readingthe present description. In a preferred approach, the measuring deviceis an ellipsometer, as the measurements made by it are fast, accurateand do not disturb and/or contact the tape bearing surface. One approachimplements an ex-situ ellipsometer where the module is removed from thetester for measurements. However, in particularly preferred approaches,an in-situ configuration may be employed so that coating thicknessmeasurements can be captured through automation in a single tool.

Transparent or substantially transparent coatings are preferably usedwith embodiments which utilize an ellipsometer. According to variousapproaches, the coating may include Diamond Like Carbon (DLC), glass,metal oxides such as alumina, chrome oxide, etc., nitrides,polycrystalline alumina, etc. or any other transparent, substantiallytransparent and/or semi-transparent coating which would be apparent toone skilled in the art upon reading the present description. However, invarious other embodiments which do not incorporate an ellipsometer, anon-transparent or substantially non-transparent coating may be used inregions where the thickness is measured.

In approaches which include alumina in the coating, it is preferablethat the alumina be deposited in a manner so that it grows in acrystalline, polycrystalline, or semi-crystalline fashion therebypreventing the tape from wearing off the coating layer too quickly. In aparticularly preferred approach, the coating is primarily e.g., at least80% up to 100%, polycrystalline alumina.

For the wear measurements to be accurate and meaningful, a coating withappropriate hardness may preferably be selected such that the differencein tape abrasivity can be easily discerned within a relatively shortperiod of time. In one approach, the coating may preferably have asimilar coefficient of friction as the module of interest such thatstiction and friction do not harm the system. This coating material maybe applied to various heads, including, but not limited to contouredheads to gauge tape abrasivity in different head structures andprofiles.

In a preferred approach, the coating may have a deposition thickness ofat least about 10 nanometers, more preferably from about 50 nanometersto about 200 nanometers, but may be higher or lower in variousembodiments.

In a variation depicted in FIG. 4B, the module 204 has a narrower tapebearing surface as measured in a direction of tape travel thereacross.An illustrative width in the direction of tape travel may beapproximately comparable to a width of the tape tents formed at thecorners of the tape bearing surface. After the tape runs for a while,the coating evolves into a stable cylindrical contour, at which point anadditional tape contact pressure term is T/RW, where T is tape tension,R is the radius of the contour, and W is the width of the tape. Thecoating 414 is thicker than in the previous approach, e.g., betweenabout 500 nm to about 5 microns. This embodiment is useful forevaluating wear resistance of thicker and/or harder coatings.

Now referring to the top down view of a head depicted in FIG, 5,according to one illustrative embodiment, the coating may include a bulkmaterial 502 and one or more sections of a second material 504 atpredetermined positions relative to the bulk material 502. Preferably,the bulk and second materials are different. In one approach, the secondmaterial 504 may include aluminum-iron-silicon (AlFeSil), Sendust, etc.In another approach, the bulk material 502 may include, but is notlimited to alumina or any other suitable material described or alludedto herein. The sections of second material may have any shape, and maybe arranged in any manner. The design depicted in FIG. 5 allows for thepossibility of differential wear which may allow for different sectionsof the coating to wear down at different rates. Moreover, thisdifferential wear may provide additional information as to the wearrates of different materials applied in different testing schemes.

Referring back to FIG. 4, in one approach, the measuring device 412 maybe configured to use areas of the tape bearing surface 209 not contactedby the tape 406 as reference gauges for the measuring. In anotherapproach, the carrier 402 and measuring device 412 may be configuredand/or positioned to allow measuring the extent of wear of the coating414 without removing the module 204 from the carrier 402.

As depicted in the cross-sectional and top down views of FIGS. 6A-6Brespectively, optionally after the initial (control) thickness t₁ ismeasured by the measuring device 412, the module 204 is positioned belowthe tape 406, and/or the tape is positioned over the module, and thetape is run across the module 204 to induce wear.

According to one embodiment as depicted in the cross-sectional and topdown views of FIGS. 7A-7B, respectively, measuring the residualthickness t₂ of the coating may include, e.g., at regular and/ornonregular intervals, creating a relative movement between the measuringdevice 412 and the module 204 (e.g., via the carrier 402) on that aportion or all of the coating 414 previously below the running tape 406becomes exposed. Then, the measuring device 412, such as anellipsometer, may measure the thickness t₂ of the coating 414 in aregion where the tape 406 has run thereacross. It is preferable thatthis residual thickness is measured near the center of the coating asmeasured in a direction of tape travel, because the coating near thecorners of the head may exhibit a wear pattern resulting from tapetenting (as seen in FIG. 7B), and thus would give inaccurate readings ifused as the residual thickness.

After the residual thickness is measured, the module 204 and carrier 402and/or tape 406 may be positioned in the operating arrangement and thetape run over the module again. This process may be repeated severaltimes.

To determine the extent of wear, the measuring device 412 may measurethe control thickness t₁ of the coating 414 in an area which never comesinto contact with tape 406, which is used as the control thickness forcomparison to the residual thickness measurement(s). This allows for anaccurate comparison between the control thickness t₁ and the residualthickness t₂ without having to unwind the head each time a coating wearmeasurement is made. In an alternate approach, noted above, the initialthickness may be measured prior to running the tape.

In further embodiments, the testing system may be operated with opposingmodules, single modules, triple modules, etc.

Depending on the abrasivity of the tape media, the coating may wear atdifferent rates. According to the embodiments described herein,measurements of the coating thickness on a module having a shape likethe module of interest reveal how quickly a certain tape media may bewearing the coating. These measurements are directly related to mediaabrasivity and how quickly the media will wear a given module ofinterest while subjected to actual product usage.

According to one approach, the wear test, according to any of theembodiments described herein, may be conducted on any newly developedcoating, e.g., to compare the characteristics of the coating with somestandard or threshold of tape head wear to evaluate the particularcoating's configuration.

Additionally, optical and/or stylus profile measurements may be taken atthe end of the test to capture the overall head profile created by thetape.

It will be clear that the various features of the foregoingmethodologies may be combined in any way, creating a plurality ofcombinations from the descriptions presented above.

It will also be clear to one skilled in the art that the methodology ofthe present invention may suitably be embodied in a logic apparatuscomprising logic to perform various steps of the methodology presentedherein, and that such logic may comprise hardware components or firmwarecomponents.

It will be equally clear to one skilled in the art that the logicarrangement in various approaches may suitably be embodied in a logicapparatus comprising logic to perform various steps of the method, andthat such logic may comprise components such as logic gates in, forexample, a programmable logic array. Such a logic arrangement mayfurther be embodied in enabling means or components for temporarily orpermanently establishing logical structures in such an array using, forexample, a virtual hardware descriptor language, which may be storedusing fixed or transmittable carrier media.

It will be appreciated that the methodology described above may alsosuitably be carried out fully or partially in software running on one ormore processors (not shown), and that the software may be provided as acomputer program element carried on any suitable data carrier (also notshown) such as a magnetic or optical computer disc. The channels for thetransmission of data likewise may include storage media of alldescriptions as well as signal carrying media, such as wired or wirelesssignal media.

Embodiments of the present invention may suitably be embodied as acomputer program product for use with a computer system. Such animplementation may comprise a series of computer readable instructionseither fixed on a tangible medium, such as a computer readable medium,for example, diskette, CD-ROM, ROM, or hard disk, or transmittable to acomputer system, via a modem or other interface device, over either atangible medium, including but not limited to optical or analoguecommunications lines, or intangibly using wireless techniques, includingbut not limited to microwave, infrared or other transmission techniques.The series of computer readable instructions embodies all or part of thefunctionality previously described herein.

Those skilled in the art will appreciate that such computer readableinstructions can be written in a number of programming languages for usewith many computer architectures or operating systems. Further, suchinstructions may be stored using any memory technology, present orfuture, including but not limited to, semiconductor, magnetic, oroptical, or transmitted using any communications technology, present orfuture, including but not limited to optical, infrared, or microwave. Itis contemplated that such a computer program product may be distributedas a removable medium with accompanying printed or electronicdocumentation, for example, shrink-wrapped software, pre-loaded with acomputer system, for example, on a system ROM or fixed disk, ordistributed from a server or electronic bulletin board over a network,for example, the Internet or World Wide Web.

Communications components such as input/output or I/O devices (includingbut not limited to keyboards, displays, pointing devices, etc.) can becoupled to the system either directly or through intervening I/Ocontrollers.

Communications components such as buses, interfaces, network adapters,etc. may also be coupled to the system to enable the data processingsystem, e.g., host, to become coupled to other data processing systemsor remote printers or storage devices through intervening private orpublic networks. Modems, cable modem and Ethernet cards are just a fewof the currently available types of network adapters.

It will be further appreciated that embodiments of the present inventionmay be provided in the form of a service deployed on behalf of acustomer to offer service on demand.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of an embodiment of the presentinvention should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

What is claimed is:
 1. A method, comprising: measuring an initialcoating thickness on a tape bearing surface of a module in a carrier;running a tape across the tape bearing surface; and at a plurality ofregular temporal intervals, measuring a residual thickness of thecoating.
 2. A method as recited in claim 1, wherein the module is partof a completed head assembly, the head assembly being received in thecarrier.
 3. A method as recited in claim 1, wherein the module is anoperative module for a tape head.
 4. A method as recited in claim 1,wherein the module is nonfunctional, wherein the measuring is performedusing an ellipsometer, wherein the coating is transparent.
 5. A methodas recited in claim 1, wherein the measuring is performed using anellipsometer.
 6. A method as recited in claim 1, further comprisingtaking stylus profile measurements.
 7. A method as recited in claim 1,further comprising, after running the tape across the tape bearingsurface, using areas of the tape bearing surface not contacted by thetape as reference gauges for the measuring.
 8. A method as recited inclaim 1, wherein the coating has a similar coefficient of friction as amodule of interest.
 9. A method as recited in claim 8, wherein themodule of interest is a functional module that is concurrently inproduction for use in a product.
 10. A method as recited in claim 1,wherein the coating has a deposition thickness of at least about 10nanometers.
 11. A method as recited in claim 1, wherein the coating istransparent.
 12. A method as recited in claim 1, wherein the coating isprimarily polycrystalline alumina.
 13. A method as recited in claim 1,wherein the initial coating thickness is measured in an area of the tapebearing surface not contacted by the tape, after running the tape acrossthe tape bearing surface.
 14. A method, comprising: measuring an initialcoating thickness on a tape bearing surface of a module in a carrier;running a tape across the tape bearing surface; and at a plurality ofregular intervals, measuring a residual thickness of the coating,wherein the coating includes a bulk material and one or more sections ofa second material at predetermined positions relative to the bulkmaterial.
 15. A method as recited in claim 14, wherein the one or moresections of the second material have defined shapes at a tape bearingsurface of the coating.
 16. A method as recited in claim 14, wherein atleast one of the sections of the second material has a rectangular shapealong a tape bearing surface of the coating, the at least one of thesections being surrounded by the bulk material along the tape bearingsurface of the coating.
 17. A method as recited in claim 14, wherein thesecond material is formed above the tape bearing surface of the moduleand has a different chemical composition than the bulk material.
 18. Amethod as recited in claim 14, wherein the second material isconstructed of a material selected from a group consisting of AlFeSiland Sendust.
 19. A method as recited in claim 14, wherein the module isnonfunctional, wherein the measuring is performed using an ellipsometer,wherein the coating is transparent.
 20. A method as recited in claim 14,wherein the initial coating thickness is measured in an area of the tapebearing surface not contacted by the tape, after running the tape acrossthe tape bearing surface.